Method for manufacturing gas adsorption base material, gas adsorption method, and gas adsorption base material

Abstract

Provided are: a method for manufacturing a gas adsorption base material capable of stably exhibiting adsorption performance with respect to volatile organic compounds and amines, more specifically, exhibiting constant adsorption performance; a gas adsorption method; and a gas adsorption base material. The method for manufacturing a gas adsorption base material includes a step of bringing a base material containing inorganic fibers, a zeolite, a pH adjuster, and a solvent into contact with each other. The pH is from 2 to 3 in the contact step. The base material is a molded body of the inorganic fibers and, in the contact step, the molded body may be brought into contact with slurry containing the zeolite, the pH adjuster, and the solvent.

Description

Gas adsorption substrate manufacturing method, gas adsorption method, and gas adsorption substrate

[0001] The present invention relates to a method for producing a gas adsorbing substrate, a gas adsorption method, and a gas adsorbing substrate.

[0002] Inorganic fibers are used to manufacture filter substrates because of their high heat resistance, high thermal insulation, and non-combustibility. Typically, inorganic fibers are formed into a sheet-like inorganic fiber sheet, which is then processed, for example, by corrugating to form a honeycomb molded body, which is then fired to obtain a filter substrate. A technique has been proposed for manufacturing honeycomb filters used for dehumidification, decomposition or removal of volatile organic compounds (VOCs), and the like, by subsequently loading an adsorbent or catalyst onto the filter substrate (see, for example, Japanese Patent Publication No. 2925127).

[0003] Patent No. 2925127

[0004] Zeolite is widely used as an adsorbent supported on a substrate. However, it has recently been discovered that the adsorption performance of VOCs and amines, especially alcohols and ammonia, varies depending on the type of zeolite-supported gas adsorption substrate.

[0005] An object of the present invention is to provide a method for producing a gas adsorption substrate, a gas adsorption method, and a gas adsorption substrate that can stably exhibit adsorption performance for volatile organic compounds and amines, i.e., that can exhibit a constant adsorption performance.

[0006] The present inventors have conducted extensive research to solve the above problems and have found that the above object can be achieved by employing the following configuration, thereby completing the present invention.

[0007] In one embodiment, the present invention relates to a method for producing a gas adsorption substrate, the method comprising a step of contacting a substrate containing inorganic fibers with zeolite, a pH adjuster, and a solvent, wherein the pH in the contacting step is 2 or more and 3 or less.

[0008] This method for producing a gas adsorption substrate reduces variation in the adsorption performance of VOCs and amines (hereinafter, collectively referred to as "VOCs, etc."), enabling efficient production of a gas adsorption substrate capable of stably exhibiting adsorption performance. While the reason for this is unclear, it is speculated as follows. After investigating the causes of destabilization of adsorption performance, the inventors came up with the idea that the cations constituting the zeolite may be responsible. When the cations of zeolite are protons (hydrogen ions), VOCs such as alcohols and amines are adsorbed relatively strongly to zeolite through hydrogen bonding. In contrast, the inventors closely examined a gas adsorption substrate with destabilized adsorption performance and found that the cations had been exchanged from protons to sodium ions. The sodium ions are believed to originate from the substrate, inorganic adhesive, adsorbent, etc. It is speculated that such cation exchange occurs during the manufacturing process of the gas adsorption substrate, reducing the hydrogen bonding ability of the zeolite with VOCs, etc., resulting in destabilization of the adsorption performance of the gas adsorption substrate. In this method for producing a gas adsorption substrate, the pH in the contact step (support step) between the substrate and zeolite is set to a low pH range of 2 or more and 3 or less to increase the hydrogen ion concentration in the contact environment, thereby suppressing the exchange of protons in the zeolite for sodium ions and making it possible to produce a gas adsorption substrate supported on zeolite with a relatively large amount of protons. As a result, the resulting gas adsorption substrate can stably exhibit adsorption performance for VOCs, etc.

[0009] In one embodiment, the substrate may be a molded body of the inorganic fibers, and in the contacting step, the molded body may be brought into contact with a slurry containing the zeolite, the pH adjuster, and the solvent.

[0010] In one embodiment, the contacting may be dipping or painting.

[0011] In one embodiment, the production method may further include a step of shaping the mixture obtained in the contacting step to obtain a shaped body.

[0012] In one embodiment, the pH adjuster is preferably an inorganic acid. Among these, the pH adjuster is preferably nitric acid. By using the above-mentioned component as the pH adjuster, a predetermined hydrogen ion concentration can be efficiently obtained in the contact environment, and damage to the firing furnace and surrounding components during firing of the base material can be reduced.

[0013] In one embodiment, the zeolite is preferably a proton-type zeolite. In addition to suppressing salt exchange from protons to sodium ions by adjusting the pH, by using a proton-type zeolite in which the cation is a proton as the slurry raw material, the proton-maintaining effect in the zeolite can be exhibited at a higher level.

[0014] In one embodiment, it is preferable to use a binder in the contact step, which allows the zeolite to be more firmly supported on the substrate, thereby stabilizing the adsorption performance of the gas adsorption substrate.

[0015] In one embodiment, the binder is preferably colloidal silica in terms of heat resistance, adhesiveness, and sodium ion reduction.

[0016] In one embodiment, the sodium ion concentration in the contact step is preferably 4000 ppm or less. By reducing the sodium ion concentration outside the zeolite, salt exchange in the zeolite can be suppressed, and the proton abundance can be increased, thereby enabling the gas adsorption substrate to stably exhibit its adsorption performance.

[0017] In one embodiment, the Na in the zeolite after the contacting step ２ The O content is preferably 0.10 mass% or less, which makes it possible to reduce the amount of sodium ions in the zeolite, in other words, to maintain the amount of protons, thereby stabilizing the adsorption performance of the gas adsorption substrate at a high level.

[0018] In one embodiment, in terms of the gas adsorption and desorption performance of the gas adsorption substrate, the formed body is preferably a honeycomb structure.

[0019] In one embodiment, the gas adsorption substrate is suitable for alcohol or amine adsorption.

[0020] In one embodiment, the present invention relates to a gas adsorption method, comprising: adsorbing an object to be adsorbed by a gas adsorption substrate manufactured by the method for manufacturing a gas adsorption substrate.

[0021] In this gas adsorption method, the exchange of protons in zeolite with sodium ions is suppressed, and the substance to be adsorbed is adsorbed using a gas adsorption substrate that supports zeolite with a relatively large amount of protons, thereby enabling efficient gas adsorption.

[0022] In one embodiment, the substance to be adsorbed is preferably an alcohol or an amine.

[0023] In one embodiment, the present invention relates to a gas adsorption substrate comprising a substrate containing inorganic fibers and zeolite supported on the substrate, the substrate having an alcohol adsorption amount of 20.0 mg / g or more as measured by the following alcohol adsorption test: (Alcohol Adsorption Test) The gas adsorption substrate was packed into a glass column and subjected to the following conditions: alcohol concentration: 100 ppm; carrier gas: air; temperature: 25°C; humidity: 65% RH; and air flow rate: 0.0045 m ３ The alcohol is adsorbed under the condition of 0.1 mg / min / min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). The alcohol concentration (mg / m) is plotted against the elapsed time t (min). ３ In the chart on which the adsorption amount (mg) is plotted, the adsorption amount (mg) in the area surrounded by the inlet concentration and the outlet concentration is integrated in the section from the start of the adsorption test (0 min) until the outlet concentration reaches the inlet concentration (100 ppm) to determine the adsorption amount (mg) of alcohol.

[0024] The gas adsorption substrate can exhibit excellent alcohol adsorption performance over time, and is suitable as an adsorption substrate for a gas adsorption system.

[0025] In one embodiment, the alcohol is preferably ethanol.

[0026] In one embodiment, the present invention relates to a gas adsorption substrate comprising a substrate containing inorganic fibers and zeolite supported on the substrate, the substrate having an amine adsorption amount of 2.0 mg / g or more as measured by the following amine adsorption test: (Amine Adsorption Test) The gas adsorption substrate is packed into a glass column under the following conditions: amine concentration: 100 ppm; carrier gas: air; temperature: 25°C; humidity: 50% RH; and air flow rate: 0.0045 m ３ The amine is adsorbed under the condition of 2000 ppm / min, and the amine concentration at the inlet (inlet concentration) and outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). The amine concentration (mg / m) is plotted against the elapsed time t (min). ３ In the chart on which the adsorption amount (mg) of the amine is plotted, the adsorption amount (mg) of the amine is calculated by integrating the adsorption amount (mg) in the area surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) until the outlet concentration reaches the inlet concentration (100 ppm).

[0027] The gas adsorption substrate can exhibit excellent amine adsorption performance over time, and is suitable as an adsorption substrate for a gas adsorption system.

[0028] In one embodiment, the amine is preferably ammonia.

[0029] 1 is a perspective view schematically showing a gas adsorption substrate according to one embodiment of the present invention; FIG. 2 is an enlarged view of part A of the open surface of the gas adsorption substrate in FIG. 1; FIG. 3 is an explanatory view showing a method for calculating the amount of ethanol adsorption; FIG. 4 is a graph showing the amount of ethanol adsorption per amount of supported zeolite in Examples and Comparative Examples; ２ 1 is a graph showing the O content. 2 is an explanatory diagram showing a method for calculating the ammonia adsorption amount. 3 is a graph showing the ammonia adsorption amount per amount of supported zeolite in Examples and Comparative Examples.

[0030] A method for producing a gas adsorption substrate, a gas adsorption method, and a gas adsorption substrate according to one embodiment of the present invention will be described below with reference to the drawings. First, the gas adsorption substrate obtained will be described, and then each step of the production method and each step of the gas adsorption method will be described. The present invention is not limited to these embodiments. In some or all of the figures, parts unnecessary for the explanation are omitted, and some parts are illustrated enlarged or reduced to facilitate the explanation. Terms indicating positional relationships, such as up and down, referred to with reference to the drawings are used merely to facilitate the explanation and are not intended to limit the configuration of the present invention in any way.

[0031] <Gas Adsorbing Substrate> Fig. 1 is a perspective view schematically showing a gas adsorbing substrate according to one embodiment of the present invention. Fig. 2 is an enlarged view of part A of the open surface of the gas adsorbing substrate in Fig. 1.

[0032] As shown in Figure 1, the gas adsorption substrate 1 is a honeycomb rotor that includes a substrate 8 containing inorganic fibers formed into the shape of the gas adsorption substrate 1, and zeolite as an adsorbent supported on the substrate 8. The honeycomb rotor is generally installed in a gas adsorption system (not shown). The gas adsorption system has a space partitioned into an adsorption zone that adsorbs substances such as VOCs, and a regeneration zone that desorbs the substances, and adsorption and regeneration are repeated as the honeycomb rotor rotates within the gas adsorption system.

[0033] The gas adsorbing substrate 1 has an internal ventilation cavity 4 formed parallel to the rotor shaft 3 for ventilating the air to be treated, regeneration air, and purge air. The gas adsorbing substrate 1 has opening surfaces 2a and 2b at both ends. The opening surfaces 2a and 2b are inlets and outlets for the air to be treated, regeneration air, and purge air. The rotor shaft 3 is attached to the center of the gas adsorbing substrate 1 and is a rotation axis for rotating the gas adsorbing substrate 1 in a rotation direction 7.

[0034] 2 , the ventilation cavity 4 is formed by alternately laminating flat portions 5 and corrugated portions 6. The gas adsorption substrate 1 has a structure in which a plurality of inorganic fiber sheets forming the flat portions 5 and a plurality of inorganic fiber sheets forming the corrugated portions 6 are laminated in a radial direction and circumferentially around the rotor shaft 3.

[0035] The pitch p of the corrugated portion 6 shown in FIG. 2 is preferably 2.0 to 3.5 mm, more preferably 2.4 to 3.1 mm. The peak height t is preferably 0.8 to 2.0 mm, more preferably 1.3 to 1.7 mm. The pitch p refers to the distance between adjacent wave peaks of the corrugated portion 6, and the peak height t refers to the height of one wave of the corrugated portion 6. The thickness (axial length) s of the gas adsorbing substrate 1 is preferably 200 to 500 mm, more preferably 300 to 450 mm. When the pitch p, peak height t, and thickness s of the gas adsorbing substrate 1 are within the above ranges, the VOC adsorption performance can be improved.

[0036] The gas adsorption substrate 1 can be efficiently produced by the following production method. The gas adsorption substrate 1 obtained by this production method is suitable as a substrate for adsorbing alcohols and amines because the exchange of protons in the zeolite with sodium ions is suppressed and zeolite with a relatively large amount of protons is supported. Examples of alcohols include lower alcohols having 1 to 5 carbon atoms, such as methanol, ethanol, and n-propanol. Examples of amines include ammonia, as well as primary to tertiary amines, such as monomethylamine, dimethylamine, trimethylamine, and triethylamine.

[0037] The gas adsorption substrate according to this embodiment has an alcohol adsorption amount of 20.0 mg / g or more in the following alcohol adsorption test. (Alcohol Adsorption Test) The gas adsorption substrate was packed into a glass column, and the alcohol concentration was 100 ppm; the carrier gas was air; the temperature was 25°C; the humidity was 65% RH; and the air volume was 0.0045 m ３ The alcohol is adsorbed under the condition of 0.1 mg / min / min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). The alcohol concentration (mg / m) is plotted against the elapsed time t (min). ３In the chart on which the adsorption amount (mg) is plotted, the adsorption amount (mg) in the area surrounded by the inlet concentration and the outlet concentration is integrated in the section from the start of the adsorption test (0 min) until the outlet concentration reaches the inlet concentration (100 ppm) to determine the adsorption amount (mg) of alcohol.

[0038] The gas adsorption substrate can exhibit excellent alcohol adsorption performance over time and is suitable as an adsorption substrate for a gas adsorption system. Details of the alcohol adsorption test are described in the Examples.

[0039] The lower limit of the alcohol adsorption amount is preferably 20.5 mg / g, more preferably 21.0 mg / g. The higher the upper limit of the alcohol adsorption amount, the better, but it may be 30.0 mg / g or 28.0 mg / g.

[0040] The alcohol can be any of the above-mentioned components as the adsorption target, but ethanol is preferred.

[0041] The gas adsorption substrate according to this embodiment has an amine adsorption amount of 2.0 mg / g or more in the following amine adsorption test. (Amine Adsorption Test) A glass column was filled with the gas adsorption substrate, and the amine concentration was 100 ppm; the carrier gas was air; the temperature was 25°C; the humidity was 50% RH; and the air volume was 0.0045 m ３ The amine is adsorbed under the condition of 2000 ppm / min, and the amine concentration at the inlet (inlet concentration) and outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). The amine concentration (mg / m) is plotted against the elapsed time t (min). ３ In the chart on which the adsorption amount (mg) of the amine is plotted, the adsorption amount (mg) of the amine is calculated by integrating the adsorption amount (mg) in the area surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) until the outlet concentration reaches the inlet concentration (100 ppm).

[0042] The gas adsorption substrate exhibits excellent amine adsorption performance over time and is suitable as an adsorption substrate for a gas adsorption system. Details of the amine adsorption test are described in the Examples.

[0043] The lower limit of the amine adsorption capacity is preferably 2.1 mg / g, more preferably 2.2 mg / g. The upper limit of the alcohol adsorption capacity is preferably as high as possible, but may be 3.0 mg / g or 2.8 mg / g.

[0044] Although the above-mentioned components can be suitably used as the amine to be adsorbed, ammonia is preferred.

[0045] <<Method for manufacturing a gas adsorption substrate>> The method for manufacturing a gas adsorption substrate according to this embodiment includes a step of contacting a substrate containing inorganic fibers with zeolite, a pH adjuster, and a solvent. The substrate may be a molded body of inorganic fibers, or may be inorganic fibers themselves. The order and operation of the contact step and molding step vary depending on the type of substrate. Each step will be described below for each type of substrate.

[0046] <First Embodiment> In this embodiment, the substrate is a molded body of inorganic fibers. In the contacting step, the molded body is brought into contact with a slurry containing zeolite, a pH adjuster, and a solvent (hereinafter also referred to as "supporting slurry"). The contacting is by immersion. That is, according to this embodiment, after forming a molded body of inorganic fibers in the molding step, the molded body is immersed in the supporting slurry in the contacting step, thereby supporting zeolite on the substrate. After the contacting step, a gas adsorption substrate can be manufactured by passing through a drying step and a calcining step.

[0047] (Molding step) In the molding step, inorganic fibers are molded to obtain a molded body. The molding step may be a single-stage or multi-stage process. The molding step also includes a process in which a plurality of molded bodies are combined to form a desired molded body. The molded body is preferably a honeycomb structure.

[0048] 1 is typically manufactured by laminating a porous flat inorganic fiber sheet and a corrugated inorganic fiber sheet obtained by corrugating the flat inorganic fiber sheet, bonding the peaks of the corrugated inorganic fiber sheet together using an inorganic adhesive. At this time, a roughly semi-cylindrical cavity formed between the flat inorganic fiber sheet and the corrugated inorganic fiber sheet serves as an air flow path, and the two sheets are laminated so that the cavity is formed in a direction parallel to the rotor shaft 3.

[0049] The inorganic fiber sheet can be formed by a known method, for example, by wet-laid nonwoven fabric processing of a sheet material slurry containing inorganic fibers. The sheet material slurry generally contains water as a medium.

[0050] The inorganic fiber is not particularly limited, and examples thereof include glass fibers such as E-glass fiber, NCR-glass fiber, ARG fiber, ECG fiber, S-glass fiber, and A-glass fiber, and chopped strands thereof, ceramic fiber, alumina fiber, mullite fiber, silica fiber, rock wool fiber, and carbon fiber.

[0051] Biosoluble inorganic fibers may be used as inorganic fibers. Biosoluble inorganic fibers are fibers that do not fall under the category of "WHO respirable fibers" or fibers that satisfy one of the following four conditions (1) to (4) according to the NotaQ "Biosoluble Fiber Determination Criteria" of EU Directive 97 / 69 / EC. Biosoluble inorganic fibers include biosoluble ceramics and biosoluble rock wool. "WHO respirable fibers" are defined by the World Health Organization (WHO) as fibrous substances that are inhaled into the body and reach the lungs, and have a length of more than 5 μm, a diameter of less than 3 μm, and an aspect ratio of more than 3. The four conditions are as follows: (1) In short-term inhalation exposure animal experiments, fibers with a length of more than 20 μm have a half-life of less than 10 days; and (2) In short-term intratracheal instillation animal experiments, fibers with a length of more than 20 μm have a half-life of less than 40 days. (3) No significant carcinogenicity in animal experiments using intraperitoneal administration. (4) No pathological findings or tumor formation associated with carcinogenicity in animal experiments using long-term inhalation exposure (however, the composition does not include alkali and alkaline earth oxides (Na２ O.K. ２ O, CaO, MgO, BaO) in an amount of more than 18% by mass.

[0052] The fiber length of the inorganic fibers is not particularly limited, but the length-weighted average fiber length of the inorganic fibers is preferably 1 to 20 mm, more preferably 2 to 10 mm, and particularly preferably 3 to 8 mm. The fiber diameter of the inorganic fibers is not particularly limited, but the average value is preferably 3 to 20 μm, more preferably 4 to 18 μm, and particularly preferably 5 to 16 μm. By setting the fiber length and fiber diameter of the inorganic fibers within the above ranges, the strength and handleability of the inorganic fiber sheet can be improved. Inorganic fibers of different fiber lengths and fiber diameters may be used in combination.

[0053] The sheet material slurry may contain components other than inorganic fibers, such as synthetic fibers, natural fibers, organic or inorganic binders, auxiliaries, additives, and fillers.

[0054] Wet papermaking can be carried out by preparing a sheet raw material slurry containing the above-mentioned components and water (medium), and then making paper from this sheet raw material slurry using a known papermaking machine. Examples of papermaking machines include cylinder papermaking machines, tilted papermaking machines, Fourdrinier papermaking machines, and short wire papermaking machines. Multi-layer papermaking can also be carried out using the same or different types of papermaking machines in combination. There are no particular restrictions on the method of dehydration and drying after papermaking, and known dryers such as Yankee dryers, cylinder dryers, air dryers, and infrared dryers can be used. There are no particular restrictions on the drying temperature, and it is usually about 100°C to 180°C.

[0055] The thickness of the inorganic fiber sheet is not particularly limited, but is preferably 50 to 300 μm, more preferably 100 to 250 μm, and particularly preferably 100 to 200 μm. A thickness within this range is preferred because it provides good corrugation properties. Furthermore, the thickness of the inorganic fiber sheet used for the flat inorganic fiber sheet and the thickness of the inorganic fiber sheet used for the corrugated inorganic fiber sheet may be the same or different.

[0056] The corrugated inorganic fiber sheet is obtained by corrugating a flat inorganic fiber sheet to form a corrugated cross section. Examples of the corrugation method include passing the flat inorganic fiber sheet through corrugated rolls.

[0057] The honeycomb structure may have any shape, but may be, for example, a laminated structure in which flat inorganic fiber sheets and corrugated inorganic fiber sheets are alternately stacked in the thickness direction, or a rotor structure obtained by winding a composite sheet in which flat inorganic fiber sheets and the peaks on one side of a corrugated inorganic fiber sheet are bonded. The rotor structure may also be formed by combining fan-shaped members obtained by dividing the honeycomb rotor into fan-shaped members in the radial direction. The fan-shaped members are obtained by alternately stacking flat inorganic fiber sheets and corrugated inorganic fiber sheets from the rotor shaft 3 toward the periphery, with the sheets on the outer periphery being slightly longer.

[0058] The flat inorganic fiber sheet and the corrugated inorganic fiber sheet can be bonded together during stacking or rolling by, for example, applying an adhesive to the peaks of the corrugated inorganic fiber sheet and then stacking or rolling the flat inorganic fiber sheet on top of it. The sector-shaped members can be bonded together by applying an adhesive to the surfaces of the sector-shaped members that correspond to the radius in a plan view and then combining multiple sector-shaped members. Examples of adhesives include inorganic adhesives such as silica sol, alumina sol, silica-alumina sol, titania sol, and cement; and organic adhesives such as acrylic resin adhesives and vinyl acetate adhesives. Among these, inorganic adhesives are preferred because they do not contain organic components and have excellent heat resistance.

[0059] Depending on the size of the gas adsorbing substrate 1, the contact step described below may be carried out on the fan-shaped members, and the gas adsorbing substrate 1 may be manufactured by combining a plurality of fan-shaped members carrying zeolite.

[0060] If necessary, a drying step may be carried out to dry the molded body. The drying method is not particularly limited, and natural drying or drying by heating may be used. Heat drying may be carried out by applying hot air at 40 to 250°C, by placing the molded body in a dryer set to the above temperature range, or by combining both.

[0061] In the contacting step, the formed body obtained in the forming step is contacted with a supporting slurry containing zeolite, a pH adjuster, and a solvent. Specifically, a supporting slurry containing predetermined components is prepared, and the formed body is immersed in the supporting slurry to perform the contacting step.

[0062] As the zeolite, zeolites known as adsorbents can be suitably used. Specific examples include Y-type zeolite, USY-type zeolite, A-type zeolite, X-type zeolite, mordenite-type zeolite, ZSM-5-type zeolite, beta-type zeolite, ferrierite-type zeolite, and L-type zeolite. One or more types of zeolites can be used in combination.

[0063] The zeolite is preferably a proton-type zeolite having protons as cations. Since not all of the protons in the proton-type zeolite are salt-exchanged, the use of the proton-type zeolite as the slurry raw material can achieve a higher level of proton retention in the zeolite.

[0064] The concentration of zeolite in the supporting slurry can be appropriately set in consideration of the efficiency of contact (support) of zeolite with the substrate, the efficiency of impregnation of the slurry into the molded body, etc. The zeolite concentration is preferably 10 to 50 mass%, more preferably 15 to 45 mass%, even more preferably 20 to 40 mass%, and particularly preferably 25 to 35 mass%.

[0065] The pH adjuster is not particularly limited as long as it can adjust the pH in the contact step to within a predetermined range, and examples thereof include inorganic acids, organic acids, and combinations thereof. Examples of inorganic acids include nitric acid, hydrochloric acid, and sulfuric acid. Examples of organic acids include sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Among these, inorganic acids are preferred, and nitric acid is particularly preferred. The pH adjuster may be added directly or in the form of a diluted solution in an amount sufficient to obtain the desired pH.

[0066] As the solvent, water or various organic solvents can be used, but water is preferred from the viewpoints of safety, low environmental impact, and solubility and dispersibility.

[0067] It is preferable to use a binder in the contact step. This allows for more solid support of the zeolite on the substrate, thereby promoting stabilization of the adsorption performance of the gas adsorption substrate. Examples of binders include inorganic binders, organic binders, and combinations thereof. Examples of inorganic binders include colloidal silica, water glass, calcium silicate, silica sol, alumina sol, titania sol, silica-alumina sol, and alkoxysilane. Examples of organic binders include thermoplastic resins such as polyethylene resin, vinyl chloride resin, (meth)acrylic acid ester resin, styrene-acrylic acid ester copolymer, vinyl acetate resin, vinyl acetate-(meth)acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, polyester resin, polyvinyl alcohol (PVA), and ethylene-vinyl alcohol copolymer; rubber emulsions such as styrene-butadiene rubber (SBR) and nitrile rubber (NBR); and thermosetting resins such as phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, polyurethane resin, and thermosetting polyimide resin. Among these, inorganic binders are preferred, and colloidal silica is particularly preferred.

[0068] The binder concentration in the supporting slurry is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and even more preferably 20 to 35% by mass.

[0069] The supporting slurry may contain other components such as a dispersant, a liquid-retaining agent, a viscosity adjuster, and a filler, if necessary.

[0070] The above components are added to water as a solvent to a predetermined concentration, and the mixture is stirred and mixed to prepare a supporting slurry.

[0071] The sodium ion concentration in the contact step is preferably 4000 ppm or less, more preferably 3500 ppm or less, even more preferably 3000 ppm or less, and particularly preferably 2500 ppm or less. By reducing the sodium ion concentration outside the zeolite, salt exchange in the zeolite can be suppressed and the proton abundance can be increased, which in turn allows the gas adsorption substrate to stably exhibit its adsorption performance.

[0072] The formed body is immersed in the prepared supporting slurry to bring the formed body into contact with the supporting slurry. The immersion time is not particularly limited and may be set appropriately taking into consideration the efficiency of supporting zeolite on the substrate. The immersion time is preferably 1 to 60 minutes, more preferably 3 to 30 minutes, and even more preferably 5 to 20 minutes.

[0073] The temperature in the contact step (the temperature of the slurry in this embodiment) is not particularly limited, and can be set appropriately within the range of 15 to 40°C.

[0074] Next, a drying step is preferably carried out to dry the molded body. Although the drying method is not particularly limited, drying by heating is preferred. Heat drying may be carried out by applying hot air at 40 to 250°C, by placing the molded body in a dryer set to the above temperature range, or by combining both.

[0075] Na in the zeolite after the contact step ２ The O content is preferably 0.10% by mass or less, more preferably 0.03% by mass or less, and even more preferably 0.01% by mass or less.

[0076] After the drying step, the compact is calcined in a calcination step to produce the gas adsorption substrate according to this embodiment. The calcination temperature is preferably 300 to 800°C, and the calcination time is preferably 0.5 to 12 hours.

[0077] The content of zeolite in the gas adsorbing substrate 1 is preferably 20 to 200 g / L in terms of gas adsorption performance, breathability, and the like.

[0078] Second Embodiment In this embodiment, the substrate is an inorganic fiber molded body. In the contacting step, the molded body is brought into contact with a supporting slurry containing zeolite, a pH adjuster, and a solvent. The contacting is by application. That is, according to this embodiment, after forming an inorganic fiber molded body in the molding step, the supporting slurry is applied to the molded body in the contacting step, thereby supporting zeolite on the substrate. The following mainly describes the differences from the first embodiment.

[0079] (Forming step) The formed body obtained in the forming step may have a sheet structure or a honeycomb structure. Considering ease of application and impregnation efficiency of the supporting slurry, the formed body preferably has a sheet structure. Note that, when the formed body is an inorganic fiber sheet having a sheet structure, it is preferable to provide a lamination step in which flat and corrugated inorganic fiber sheets are laminated to form a honeycomb structure after the contact step described below.

[0080] (Contacting step) Examples of a method for applying the supporting slurry to the molded body include spray coating, curtain coating, impregnation coating, bar coating, roll coating, and blade coating. The amount of coating may be adjusted so that the zeolite content in the final gas adsorption substrate is the target amount. The number of coatings is not particularly limited, and may be one or more than two coatings.

[0081] Next, a drying step and a calcination step are carried out to produce a gas adsorbing substrate. When the molded body has a sheet structure, it is preferable to provide a lamination step between the drying step and the calcination step.

[0082] Third Embodiment In this embodiment, the substrate is inorganic fibers themselves. In the contacting step, the inorganic fibers as the substrate are contacted with a support slurry containing zeolite, a pH adjuster, and a solvent to obtain a mixture. Further, a step of molding the mixture obtained in the contacting step to obtain a molded body is performed. That is, according to this embodiment, zeolite is supported on inorganic fibers in the contacting step, and a molded body of inorganic fibers supporting zeolite is formed in the subsequent molding step. Below, differences from the first embodiment will be mainly described.

[0083] (Contacting Step) A predetermined amount of inorganic fibers is added to the support slurry and stirred and mixed to obtain a mixture. The mixing time is not particularly limited, and may be approximately 0.1 to 10 minutes. The content of inorganic fibers in the mixture is preferably 6 to 45% by mass, more preferably 8 to 35% by mass, and even more preferably 10 to 25% by mass. The content of zeolite in the mixture may be the same as or different from the content of zeolite in the support slurry in the first embodiment.

[0084] (Forming process) Instead of the sheet raw material slurry of the first embodiment, the mixture obtained above can be wet-laid to form a nonwoven fabric, thereby producing a formed body (inorganic fiber sheet) having a sheet structure. Thereafter, a drying process may be performed as necessary. Furthermore, it is preferable to perform a lamination process in which flat and corrugated inorganic fiber sheets are laminated to form a honeycomb structure.

[0085] Next, the honeycomb structure is subjected to a firing step, whereby a gas adsorption substrate can be manufactured.

[0086] <<Gas Adsorption Method>> The gas adsorption method according to this embodiment includes the step of adsorbing an object to be adsorbed by a gas adsorbing substrate manufactured by the method for manufacturing a gas adsorbing substrate.

[0087] In this gas adsorption method, the exchange of protons in the zeolite with sodium ions is suppressed, and the substance to be adsorbed is adsorbed using a gas adsorption substrate that supports zeolite with a relatively large amount of protons, so that efficient gas adsorption can be performed over time.

[0088] The substance to be adsorbed is preferably an alcohol or an amine. Suitable examples of alcohols and amines include the components described above.

[0089] Examples of the carrier gas in the adsorption step include air and inert gases such as nitrogen gas and argon gas.

[0090] The temperature, humidity, flow rate, etc. in the adsorption step may be appropriately set taking into consideration the substance to be adsorbed, adsorption efficiency, etc.

[0091] After the adsorption step, a desorption step for desorbing the adsorption target may be performed to regenerate the gas adsorption substrate. In the desorption step, the gas adsorption substrate may be heated, a desorption gas (air, etc.) may be circulated, or heating of the gas adsorption substrate and circulating a desorption gas may be combined. The adsorption step and the desorption step may be repeated.

[0092] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0093] Example A carrier made of a silica-alumina fiber sheet (thickness 0.2 mm) having a corrugated honeycomb structure with a pitch of 3.3 mm and a peak height of 1.6 mm was cut into a cylindrical shape with a diameter of 200 mm and a thickness of 20 mm to obtain a substrate.

[0094] Separately, 16.2 parts by mass of ZSM-5 zeolite (proton type), 16.2 parts by mass of ZSM-5 zeolite (sodium ion type), 35.5 parts by mass of colloidal silica, and 32.1 parts by mass of water were mixed, and nitric acid was added to adjust the pH to 2.5 to obtain a supporting slurry.

[0095] A substrate was immersed in the supporting slurry, dried, and then calcined to obtain a gas adsorbing substrate.

[0096] Comparative Example A gas adsorbing substrate was obtained in the same manner as in Example, except that nitric acid was not added in preparing the support slurry.

[0097] <Evaluation: Ethanol Adsorption Test> Using the gas adsorption substrates of the Examples and Comparative Examples, an ethanol adsorption test was carried out according to the following procedure.

[0098] <Ethanol Adsorption Test> A glass column was filled with a gas adsorption substrate. The ethanol concentration was 100 ppm; carrier gas was air; temperature was 25°C; humidity was 65% RH; and air volume was 0.0045 m ３ The adsorption test was carried out by adsorbing ethanol at a rate of 100 ppm / min and measuring the ethanol concentration at the inlet (inlet concentration) and outlet (outlet concentration) of the column. The adsorption test was carried out until the adsorption capacity of the zeolite was saturated. Specifically, the adsorption test was carried out until the outlet concentration reached the inlet concentration (100 ppm).

[0099] The amount of ethanol adsorption was calculated by the following procedure. Figure 3 is an explanatory diagram showing the method for calculating the amount of ethanol adsorption. First, ethanol gas was passed through the gas adsorption substrate under the above conditions, and the inlet and outlet concentrations were measured over time using a hydrocarbon meter (Shimadzu Corporation, "VMS-1000F"). Next, the measured concentration (ppm) was converted into mg / m ３ As a result, the ethanol concentration (mg / m) was calculated with respect to the elapsed time t (min) as shown in FIG. ３ In this chart, minute sections were set every 0.05 min, and the area surrounded by the inlet concentration and outlet concentration in each minute section was assumed to be a trapezoid (the lightly shaded trapezoid in Figure 3). The area (unit volume (m ３ The amount of adsorption (mg) per unit area and air volume (m ３ / min) was calculated, and this was defined as the amount of adsorption (mg) in the minute interval. Finally, the amount of adsorption (mg) in the minute interval was integrated over the interval from the start of the adsorption test (0 min) until the outlet concentration reached the inlet concentration (100 ppm) to determine the amount of ethanol adsorbed (mg).

[0100] The amount of ethanol adsorbed per amount of supported zeolite was then calculated using the following calculation formula. The results are shown in Figure 4. Figure 4 is a graph showing the amount of ethanol adsorbed per amount of supported zeolite for Examples and Comparative Examples. <Calculation formula> Amount of supported zeolite: A (g) Amount of ethanol adsorbed: B (mg) Amount of ethanol adsorbed per amount of supported zeolite: C = B / A (mg / g)

[0101] As a result, the adsorption capacity was 21.3 mg / g in the Example, while it was 16.2 mg / g in the Comparative Example, and the gas adsorption substrates of the Example showed excellent adsorption performance. This is presumably because, in the Example, the pH of the support slurry was adjusted to 2.5, so that the cations of the sodium ion-type zeolite were exchanged with protons and the zeolite was supported on the gas adsorption substrate in the state of proton-type zeolite, whereas in the Comparative Example, the cations of the sodium ion-type zeolite were not sufficiently exchanged with protons and the zeolite was supported in the state of sodium ion-type.

[0102] <Evaluation: Cation Exchange Evaluation Test> For each of the supporting slurries prepared in the Examples and Comparative Examples, the Na content in the zeolite was measured after stirring for 1 hour after preparation. ２ The O content was measured. Specifically, the prepared support slurry was stirred for 1 hour and then filtered to collect the zeolite. The collected zeolite was thoroughly washed with ion-exchanged water and dried to obtain a measurement sample. The measurement sample was subjected to X-ray fluorescence analysis (XRF) to determine the Na content. ２ The O content (mass%) was calculated. The results are shown in Figure 5. Figure 5 shows the Na content in the zeolites of the Examples and Comparative Examples. ２ 1 is a graph showing the O content.

[0103] In the supporting slurry of the example, although the sodium ion type zeolite was used in the same amount as the proton type zeolite, an extremely low Na ２ The O content was 0.10% by mass or less. This is presumably due to the exchange of cations of the added sodium ion type zeolite with protons. On the other hand, in the supporting slurry of the comparative example, Na ２ This is presumably because the O content was high and the cations of the sodium ion type zeolite were not sufficiently exchanged with protons.

[0104] <Evaluation: Ammonia Adsorption Test> An ammonia adsorption test was carried out using the gas adsorption substrates of the Examples and Comparative Examples according to the following procedure.

[0105] <Ammonia Adsorption Test> Ammonia concentration: 100 ppm; carrier gas: air; temperature: 25°C; humidity: 50% RH; air volume: 0.0045 m was measured on a gas adsorption substrate packed in a glass column. ３ The adsorption test was carried out by adsorbing ammonia under the condition of 100 ppm / min and measuring the ammonia concentration at the inlet (inlet concentration) and the ammonia concentration at the outlet (outlet concentration). The adsorption test was carried out until the adsorption capacity of the zeolite was saturated. Specifically, the adsorption test was carried out until the outlet concentration reached the inlet concentration (100 ppm).

[0106] The ammonia adsorption amount was calculated by the following procedure. Figure 6 is an explanatory diagram showing the calculation method for the ammonia adsorption amount. First, ammonia gas was passed through the gas adsorption substrate under the above conditions, and the inlet and outlet concentrations were measured over time using a detector tube (ammonia detector tubes "3La", "3L" and "3S" manufactured by Gastec Corporation). Next, the measured concentrations (ppm) were converted into mg / m ３ As a result, the ammonia concentration (mg / m) was calculated with respect to the elapsed time t (min) as shown in FIG. ３ In this chart, minute sections were set every minute, and the area surrounded by the inlet concentration and outlet concentration in each minute section was assumed to be a trapezoid (the lightly shaded trapezoid in Figure 6). The area (unit volume (m ３ The amount of adsorption (mg) per unit area and air volume (m ３ / min) was calculated, and this was defined as the adsorption amount (mg) in the minute section. Finally, the adsorption amount (mg) in the minute section was integrated over the section from the start of the adsorption test (0 min) until the outlet concentration reached the inlet concentration (100 ppm) to determine the ammonia adsorption amount (mg).

[0107] Thereafter, the ammonia adsorption amount per amount of supported zeolite was calculated using the following calculation formula. The results are shown in Figure 7. Figure 7 is a graph showing the ammonia adsorption amount per amount of supported zeolite for Examples and Comparative Examples. <Calculation formula> Amount of supported zeolite: A (g) Ammonia adsorption amount: B (mg) Ammonia adsorption amount per amount of supported zeolite: C = B / A (mg / g)

[0108] As a result, the adsorption capacity was 2.36 mg / g in the Example, while it was 1.19 mg / g in the Comparative Example, indicating that the gas adsorption substrates of the Example exhibited excellent adsorption performance. The reason for this is the same as that considered in the ethanol adsorption test. That is, it is presumed that this is because, in the Example, the pH of the support slurry was adjusted to 2.5, so that the cations of the sodium ion-type zeolite were exchanged with protons, and the zeolite was supported on the gas adsorption substrate in the state of proton-type zeolite, whereas in the Comparative Example, the cations of the sodium ion-type zeolite were not sufficiently exchanged with protons, and the zeolite was supported in the state of sodium ion-type.

[0109] REFERENCE SIGNS LIST 1 Gas adsorption substrate 2a, 2b Opening surface 3 Rotor shaft 4 Ventilation cavity 5 Flat portion 6 Corrugated portion 7 Rotation direction 8 Substrate p Pitch t Height of peaks s Thickness

Claims

1. A method for producing a gas adsorption substrate, comprising the step of contacting a substrate containing inorganic fibers with zeolite, a pH adjuster, and a solvent, wherein the pH in the contacting step is 2 or more and 3 or less.

2. The method for producing a gas adsorption substrate according to claim 1, wherein the substrate is a molded body of the inorganic fiber, and in the contacting step, the molded body is contacted with a slurry containing the zeolite, the pH adjuster, and the solvent.

3. The method for producing a gas adsorption substrate according to claim 2, wherein the contact is by immersion or coating.

4. The method for producing a gas adsorbing substrate according to claim 1, further comprising a step of forming the mixture obtained in the contact step to obtain a formed body.

5. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the pH adjuster is an inorganic acid.

6. The method for producing a gas adsorbing substrate according to claim 5, wherein the pH adjuster is nitric acid.

7. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the zeolite is a proton type zeolite.

8. The method for producing a gas adsorbing substrate according to any one of claims 1 to 4, wherein a binder is allowed to coexist in the contact step.

9. The method for producing a gas adsorbing substrate according to claim 8, wherein the binder is colloidal silica.

10. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the sodium ion concentration in the contact step is 4000 ppm or less.

11. Na in the zeolite after the contact step ２ The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the O content is 0.10 mass% or less.

12. The method for producing a gas adsorbing substrate according to any one of claims 2 to 4, wherein the formed body is a honeycomb structure.

13. The method for producing a gas adsorbing substrate according to any one of claims 1 to 4, wherein the gas adsorbing substrate is for adsorbing alcohol or amine.

14. A gas adsorption method comprising the step of adsorbing an object to be adsorbed by a gas adsorption substrate manufactured by the method for manufacturing a gas adsorption substrate as described in claim 1.

15. The gas adsorption method according to claim 14, wherein the substance to be adsorbed is an alcohol or an amine.

16. A gas adsorption substrate comprising a substrate containing inorganic fibers and zeolite supported on the substrate, the substrate having an alcohol adsorption amount of 20.0 mg / g or more as determined by the following alcohol adsorption test. (Alcohol Adsorption Test) A gas adsorption substrate packed in a glass column was subjected to the following test: alcohol concentration: 100 ppm; carrier gas: air; Temperature: 25℃; Humidity: 65%RH; Air volume: 0.0045m ３ Alcohol is adsorbed under conditions of 100 ppm / min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is continued until the outlet concentration reaches the inlet concentration (100 ppm). The alcohol concentration (mg / m ３ ), the amount of alcohol adsorbed (mg) is calculated by integrating the amount of adsorption (mg) in the area surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) until the outlet concentration reaches the inlet concentration (100 ppm).

17. The gas adsorbing substrate according to claim 16, wherein the alcohol is ethanol.

18. A gas adsorption substrate comprising a substrate containing inorganic fibers and zeolite supported on the substrate, the substrate having an amine adsorption amount of 2.0 mg / g or more as determined by the following amine adsorption test. (Amine adsorption test) A glass column is filled with the gas adsorption substrate, and the amine concentration is 100 ppm; carrier gas: air; Temperature: 25℃; Humidity: 50%RH; Air volume: 0.0045m ３ The amine is adsorbed under the condition of 100 ppm / min, and the amine concentration at the inlet (inlet concentration) and the amine concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). The amine concentration (mg / m ３ ) is plotted, the adsorption amount (mg) in the portion surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the time when the outlet concentration reaches the inlet concentration (100 ppm) is integrated to determine the amine adsorption amount (mg).

19. The gas adsorbing substrate of claim 18, wherein the amine is ammonia.

Images